RU2808296C1 - Method for preparing prefabricated defects in form of cracks in additive manufacturing of metal parts and prefabricated part manufactured by this method - Google Patents

Abstract

FIELD: additive manufacturing.

SUBSTANCE: invention is related to methods for preparing prefabricated defects in form of cracks and embedded defects in form of cracks and their prefabricated parts. A method for preparing prefabricated defects in form of cracks comprises setting a defect zone, setting the volume percentage of defects in form of cracks in the defect zone, adjusting the proportion of spherical powder, the proportion of hollow powder and parameters of the defect preparation process according to the volume percentage of defects in form of cracks based on the laser melting deposition method, layer-by-layer printing of the defect zone using defect preparation powder and defect preparation process parameters. The particle size of defect preparation powder is from 45 mcm to 150 mcm, the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%. The defect preparation process parameters include: laser power 450-550 W, scanning speed 600-1200 mm/min, powder feed rate 4-12 g/min, spot diameter 1-1.2 mm, scanning step 0.5-0.8 mm and layer thickness 0.08-0.2 mm.

EFFECT: group of inventions provides methods for preparing prefabricated defects in the form of cracks to provide effective control of the position and proportion of defects generated in a prefabricated part.

13 cl, 8 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The invention relates to the field of additive manufacturing and, in particular, to methods for preparing prefabricated crack defects and embedded crack defects, and prefabricated parts thereof.

BACKGROUND OF THE ART

Additive manufacturing (AM) technology is commonly known as 3D printing (three-dimensional printing) technology. Nowadays, additive manufacturing of metal products is becoming more and more developed and widely applied in aerospace, medical equipment, automotive, nuclear power, etc. Among them, laser melting deposition (LMD) method based on synchronous powder feeding is a popular additive manufacturing technology, where the powder is transported by a carrier gas to coalesce into a spherical powder, high-energy laser beams are used to melt the metal powder, which is simultaneously transported and coalesced to form moving pools of molten metal in an unstable state, small pools of melt quickly solidify due to a large temperature gradient, melt and accumulate layer by layer and finally form into a solid part. This technology is typically used in the rapid formation of large and complex aerospace and military metal structures with low cost and short cycle times, or the rapid remanufacturing of high value-added components such as aircraft engine mounting section system, rear section platform, bladed disk, turbine blades and other parts.

The process of metal formation/recovery by laser melting deposition based on synchronous powder supply involves the combination of several fields, for example, a temperature field and a stress field, which is a complex non-equilibrium solidification process with a large number of instability factors. It is not possible to avoid the occurrence of defects of various types and sizes, and pores, cracks and lack of fusion can usually be detected. Due to the anisotropic structure and characteristics of an additively manufactured product and differences from products produced by traditional methods of casting, forging, welding and others, the generated defects also differ. Traditional defect detection and evaluation methods are generally not suitable for additive manufacturing. Thus, preparing a standard additive manufacturing part with defects, a defect sample, or a defect part allows not only to prepare for accurate non-destructive testing of defects, but also to accurately carry out qualitative and quantitative research on defects generated in additive manufacturing, accurately simulating the effect of defects of different types or sizes on the mechanical properties of parts obtained by forming/restoring in the additive manufacturing of metal products, to further study and confirm the influence of defects and the reliability of additive manufacturing parts, which is of great importance for the application of additive manufacturing parts in aerospace and other fields.

A crack defect is a crack that occurs due to the breakdown of an atomic bond and the formation of a crack at a new interface in the material. Typically, defects in the form of cracks on the surface of components are easy to detect and observe. However, for crack defects inside components, due to the stress concentration effect at the tip of the crack, the crack will initiate and propagate, significantly degrading the mechanical performance of the material and negatively affecting the service life of the part. To prepare a metal product with built-in defects in the form of cracks, three methods are currently known. The first is to use a fatigue testing apparatus to carry out fatigue testing to form defects in the form of cracks of a certain size. The second consists of cutting cracks with a plasma or other high-energy beam and then welding them. The third involves the use of selective laser melting (SLM) directly to 3D print defects in the form of cracks with the expected contour and size and directly form a product with the feature of a defect in the form of cracks inside. A product with defects in the form of cracks, prepared by the first and second methods, causes different degrees of damage to the structure and characteristics of the product. A product with defects in the form of cracks prepared by the third method not only breaks the continuity of the structure, but can also likely cause powder with a particle diameter of tens of microns to remain in the crack if the width of the crack is relatively large, or the crack is likely filled with molten metal of the boundary contour if the width of the crack is relatively small and the crack cannot form. The above three methods do not accurately model the features of crack defects generated during the solidification process of a product, do not accurately represent the structural features of crack defects, and do not allow an accurate and efficient assessment of the relationship between defects and mechanical properties.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a method for preparing prefabricated crack defects to effectively control the position and proportion of defects generated in a prefabricated part.

It is yet another object of the present invention to provide a method for preparing a prefabricated part with embedded crack defects to effectively evaluate the relationship between the crack defects within the prefabricated part and the mechanical performance of the prefabricated part.

It is yet another object of the present invention to provide a prefabricated part with embedded crack defects, where the prefabricated part is prepared by the above-mentioned method.

It is yet another object of the present invention to provide a method for preparing a remanufactured part with embedded crack defects to effectively evaluate the relationship between the crack defects within the remanufactured part and the mechanical performance of the remanufactured part.

To solve the above problem, a method for preparing prefabricated defects in the form of cracks contains:

setting the defect zone,

setting the volume percentage of defects in the form of cracks in the defect zone,

adjusting the proportion of spherical powder, the proportion of hollow powder and the parameters of the defect preparation process according to the volume percentage of defects in the form of cracks,

based on the laser melting deposition method, layer-by-layer printing of the defect zone using defect preparation powder and defect preparation process parameters,

where the particle size of the defect preparation powder is from 45 µm to 150 µm, the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%,

The defect preparation process parameters contain: laser power 450 W - 550 W, scanning speed 600 mm/min - 1200 mm/min, powder feed rate 4 g/min - 12 g/min, spot diameter 1 mm - 1.2 mm, step scanning 0.5 mm - 0.8 mm and layer thickness 0.08 mm - 0.2 mm.

In one or more embodiments, a method for preparing prefabricated crack defects comprises:

control of the volume percentage of defects in the form of cracks in the defect zone by adjusting the ratio of laser power P to scanning speed v,

Moreover, when the P/v ratio decreases, the volume percentage of defects in the form of cracks in the defect zone increases.

To solve another problem mentioned above, a method for preparing a prefabricated part with built-in defects in the form of cracks, based on a laser melting deposition method, contains:

obtaining a 3D model of a pre-fabricated part,

dividing the prefabricated part into at least one defect zone and one forming zone, wherein the defect zone is provided within the prefabricated part,

setting the volume percentage of built-in defects in the form of cracks in the defect zone,

adjusting the proportion of spherical powder, the proportion of hollow powder and the parameters of the defect preparation process according to the volume percentage of defects in the form of cracks,

layer-by-layer printing of a prefabricated part with embedded crack defects, where the defect preparation powder and defect preparation process parameters are used to print specific layers relative to the defect area,

where the particle size of the defect preparation powder is from 45 µm to 150 µm, where the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%,

The defect preparation process parameters contain: laser power 450 W - 550 W, scanning speed 600 mm/min - 1200 mm/min, powder feed rate 4 g/min - 12 g/min, spot diameter 1 mm - 1.2 mm, pitch scanning 0.5 mm - 0.8 mm and layer thickness 0.08 mm - 0.2 mm.

In one or more embodiments, the 3D model of a prefabricated part is divided into a plurality of defect zones and a forming zone, where the proportion of spherical powder, the proportion of hollow powder, and defect preparation process parameters are set separately for each defect zone.

In one or more embodiments, a method of preparing a prefabricated part with embedded crack defects comprises: controlling the volume percentage of crack defects in a defect zone by adjusting the ratio of laser power P to scanning speed v,

Moreover, when the P/v ratio decreases, the volume percentage of defects in the form of cracks in the defect zone increases.

In one or more embodiments, the method of preparing a prefabricated part with embedded crack defects further comprises:

processing of 3D models of the defect zone and formation zone, where the model processing contains:

processing of adding a tolerance,

layer separation and cutting processing and

path planning processing.

In one or more embodiments, the method of preparing a prefabricated part with embedded crack defects further comprises:

heat treatment of the printed pre-fabricated part,

removing the printed prefabricated part from the substrates and

surface treatment of a printed prefabricated part.

To solve another problem mentioned above, a prefabricated part with built-in defects in the form of cracks is prepared in the above-mentioned manner.

To solve another aforementioned problem, a method for preparing a repaired part with embedded defects in the form of cracks, based on a laser melting deposition method, wherein the restored part comprises a part body and a restoration zone, wherein the restoration zone is used to repair the defect or damage to the part body, wherein the method comprises:

obtaining a 3D model of the part body and restoration zone, respectively,

receiving the body of the part,

dividing the 3D model of the restoration zone into at least one defect zone and one formation zone, where the defect zone is provided inside the restored part after restoration,

setting the volume percentage of built-in defects in the form of cracks in the defect zone,

adjusting the proportion of spherical powder, the proportion of hollow powder and the parameters of the defect preparation process according to the volume percentage of defects in the form of cracks,

layer-by-layer printing of a restoration zone on a defect in the body of a part, where defect preparation powder and defect preparation process parameters are used to print specific layers relative to the defect zone,

where the particle size of the defect preparation powder is from 45 µm to 150 µm, where the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%,

The defect preparation process parameters contain: laser power 450 W - 550 W, scanning speed 600 mm/min - 1200 mm/min, powder feed rate 4 g/min - 12 g/min, spot diameter 1 mm - 1.2 mm, step scanning 0.5 mm - 0.8 mm and layer thickness 0.08 mm - 0.2 mm.

In one or more embodiments, a method for preparing a remanufactured part with embedded crack defects comprises:

control of the volume percentage of defects in the form of cracks in the defect zone by adjusting the ratio of laser power P to scanning speed v,

Moreover, when the P/v ratio decreases, the volume percentage of defects in the form of cracks in the defect zone increases.

In one or more embodiments, the part body defect includes casting defects, machining defects, or performance defects, and the method further comprises:

cutting through a finished part to produce the body of the part.

In one or more embodiments, the method of preparing a remanufactured part with embedded crack defects further comprises:

processing of 3D models of the defect zone and the formation zone of the restoration zone, where the model processing contains:

processing adding tolerance,

layer separation and cutting processing and

path planning processing.

In one or more embodiments, the method of preparing a remanufactured part with embedded crack defects further comprises:

heat treatment of the printed restored part and

surface treatment of the printed restored part.

The advantages of the invention are that: simulating crack defects inside a remanufactured part with embedded crack defects is achieved according to the above-mentioned embodiment, which makes it possible to obtain a remanufactured part with naturally generated crack defects to further analyze the relationship between the embedded crack defects cracks and reliability of the remanufactured part prepared by additive manufacturing, providing strong theoretical support for the application of metal additive manufacturing forming, which has a broad research and application perspective.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific features and implementation of the present invention are further described in the following embodiments and drawings.

FIG. 1 is a schematic view of a prefabricated part with embedded crack defects in one embodiment.

FIG. 2 is a schematic cross-sectional view of a prefabricated part including a defect area and a forming area.

FIG. 3 is a flowchart of a method for preparing the prefabricated part shown in FIG. 1.

FIG. 4 is a polished metallographic morphology of crack defects on a prefabricated part prepared in one embodiment.

FIG. 5 is a schematic cross-sectional view of a defect area of a remanufactured part with embedded crack defects in another embodiment.

FIG. 6 is a schematic cross-sectional view of the recovery zone.

FIG. 7 is a flowchart of the method for preparing the remanufactured part shown in FIG. 5.

FIG. 8 is a polished metallographic morphology of crack defects on a prefabricated part prepared in another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments for implementing this technical solution are disclosed below. To simplify the disclosure, specific examples of each element and arrangement are described below. Of course, these embodiments are illustrative only and are not intended to limit the scope of the present application. For example, the first feature described below in the specification is formed above or on the second feature, and an embodiment is possible in which the first and second features are formed by direct connection, or an embodiment is possible in which additional features are formed between the first and second features, from -why the first and second features may not be directly connected. In addition, reference numerals and/or letters may be repeated in various embodiments of the invention. Repeated reference numerals and/or letters are for brevity and clarity and do not indicate the relationship between the various embodiments and/or structures contemplated. Additionally, when the first element is described as being connected or combined with a second element, the description includes an embodiment in which the first and second elements are directly connected or combined with each other, and also includes the use of one or more other intermediate elements to be added, therefore the first and the second elements are connected or combined with each other indirectly.

It should be noted that the words "up", "down", "left", "right", "front", "rear", "top", "bottom", "positive", "negative", "clockwise" and "counterclockwise" in the following description are used for convenience only, and do not imply any particular fixed direction. In fact, they are used to express the relative position and/or orientation between different parts of an object.

It should be noted that these and other subsequent drawings are for exemplary purposes only and are not to scale and should not be construed as limiting the scope of protection actually required by the present invention. Moreover, methods adapted to different embodiments can be suitably combined.

One aspect of the invention is to provide a method for preparing prefabricated crack defects. Preparation of defects in the form of cracks is achieved in the following steps.

First of all, when specifying a defect area, it should be understood that the defect area mentioned in this invention means an area where crack defects will be prefabricated, which may be a portion of a part to be printed, for example, a partial area on the surface of a part or a partial area inside the part, or the complete part, whereby the complete part is considered as a defect zone.

Then, set the volume percentage of crack defects in the defect area, and adjust the proportion of spherical powder, hollow powder proportion and defect preparation process parameters according to the volume percentage of crack defects.

Then, based on the laser melting deposition method, layer-by-layer printing of the defect area using the defect preparation powder and defect preparation process parameters. It should be understood that the defect preparation powder referred to in this invention means the specific powder used to print the defect area, and the defect preparation process parameters mean the specific printing parameters used to print the defect area. In particular, the type, chemical composition and physical properties of the defect preparation powder may be the same or different than for the powder used for normal printing of the formation zone, and the powder preparation process may be the same or different, that is, for the defect zone and the formation zone the same powder can be used provided that the preparation process is different. The defect preparation powder and defect preparation process parameters are described in detail below.

The particle size of defect preparation powder ranges from 45 µm to 150 µm, where the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%. It should be noted that the particle size referred to in this invention means the particle size of the powder, and the particle size of a spherical powder is usually expressed by its diameter. For an irregularly shaped particle, the diameter of a spherical particle that behaves the same as an irregularly shaped particle can be thought of as the equivalent diameter of that particle. The particle size distribution of a powder can be measured by a dry sieving method or a wet method using a laser particle size analyzer. The proportion of spherical powder means the ratio of the amount of spherical powder to the total amount of defect preparation powder. Powder particle materials used for additive manufacturing have different shapes, such as spherical powder with a spherical shape and a smooth surface, or satellite powder formed by two or more spherical powder particles bonded to each other, with a raised structure on the surface and a rough spherical shape , or other irregularly shaped powder, such as strip, rod, sheet, etc. The proportion of hollow powder means the ratio of the amount of hollow powder to the total amount of defect preparation powder, these powders used as powder materials for additive manufacturing with pores inside, and the hollow form is referred to as hollow powder. It should be understood that the ratio of spherical powder to defect preparation powder depends on the outer contour of the powder particles, while the ratio of hollow powder to defect preparation powder depends on whether the powder particles have pores inside and are in a hollow form.

The defect preparation process parameters contain: laser power 450 W - 550 W, scanning speed 600 mm/min - 1200 mm/min, powder feed rate 4 g/min - 12 g/min, spot diameter 1 mm - 1.2 mm, step scanning 0.5 mm - 0.8 mm and layer thickness 0.08 mm - 0.2 mm.

The volume percentage of defects in the form of cracks in the defect zone is controlled by adjusting the parameters of the defect preparation process. It should be understood that the volume percentage of crack defects in the defect zone mentioned in this invention means the ratio of the volume of crack defects to the volume of the defect zone.

Specifically, in one embodiment, the volume percentage of crack defects in the defect zone is controlled by adjusting the ratio of the laser power P to the scanning speed v, when the ratio P/v decreases, the volume percentage of crack defects in the defect zone increases, thus the volume percentage of defects in the form of cracks in the defect zone can increase by reducing the ratio of laser power to scanning speed. In another embodiment, the method for adjusting the defect preparation process parameters is determined by trial and error, for example, parameter A is adjusted in the (N+1)th test, the volume percentage of crack defects prepared in the (N+1)th test, shows an increasing trend compared to the volume percentage of crack defects prepared in the Nth test, allowing a calibrated volume percentage to be obtained by continuously adjusting parameter A. In another embodiment, a parametric database may also be provided to record the change in the percentage of defects in in the form of cracks every time after adjusting the parameters of the defect preparation process, therefore, a certain proportion of defects in the form of cracks can be obtained by accessing the database to adjust the parameters of the defect preparation process. When the prefabricated volume percentage of crack defects in the defect zone is in the range of 0.01%-1.5%, the relationship between the volume percentage of crack defects in the defect zone and the P/v ratio is expressed as follows:

Volume percentage of defects in the form of cracks in the defect zone=-0.014ln（P/v）+0.001.

Crack defects prepared by this method are naturally generated during the printing process, which allows the continuity feature corresponding to the structure of the crack zone to be maintained, and the specific fraction of crack defects can be obtained by adjusting the parameters of the defect preparation process, providing a basis for further consideration of the relationship between defects in the form of cracks and influence on mechanical properties.

For a further embodiment of the crack preparation method, the first and second embodiments are shown below to illustrate a specific crack preparation method.

First embodiment

The first embodiment demonstrates a method for preparing a prefabricated part with embedded crack defects and a prefabricated part with embedded crack defects prepared using this method. It should be understood that an embedded crack defect means a crack defect created within a prefabricated part.

FIG. 1 shows a schematic view of a prefabricated part with built-in crack defects in this embodiment, FIG. 2 shows a schematic cross-sectional view of a prefabricated part including a defect zone and a formation zone, FIG. 3 shows a block an operation diagram of a method for preparing a prefabricated part shown in FIG. 1.

According to FIG. 1 and FIG. 3, to prepare the prefabricated part 1 shown in FIG. 1, S100 is first performed: obtain a 3D model of the prefabricated part 1, in particular, a 3D model of the prefabricated part 1 for additive manufacturing can be obtained by 3D scanning, etc., the 3D model can be created in 3D graphics processing software, such as UG, AUTOCAD or other modeling software.

Next, S101 is performed: dividing the prefabricated part 1 into a defect zone 10 and a forming zone 11, wherein the formation zone 11 referred to in this invention means the remaining portion of the part excluding the defect zone 10. While FIG. 1 shows, by way of example only, one defect zone 10 separated from the prefabricated part 1, it should be understood that the number of defect zones 10 may be two or more. In this embodiment, the areas of the prefabricated part 1 except for the defect area 10 can be considered as a whole as the formation area 11.

The defect zone 10 is provided inside the prefabricated part 1, it should be understood that, the built-in crack defects are generated within the structure of the part in the actual printing process, which makes it possible to achieve the preparation of the prefabricated part 1 with built-in crack defects by defining the defect zone 10 inside in advance manufactured part 1.

Next, S102 is executed: set the volume percentage of built-in crack defects in the defect area 10, wherein the volume percentage may be determined by the ratio of the volume of built-in crack defects in the actual printed part to be modeled to the volume of the actual printed part, that is, (volume of built-in cracks in the form of cracks/volume of the defect area) * volume of the defect area/volume of the prefabricated part=volume of built-in defects in the form of cracks in the actual printed part/volume of the actual printed part. If the number of defect zones 10 in the prefabricated part 1 is greater than one, by dividing the prefabricated part 1 into a defect zone 10 and a forming zone 11 in step S101, defects in the prefabricated part 1 can be quickly and accurately prepared according to the actual volume percentage. At the same time, the proportion of spherical powder, the proportion of hollow powder and the defect preparation process parameters can be adjusted according to the volume percentage of defects.

Then S104 is executed: layer-by-layer printing of prefabricated part 1 with built-in defects in the form of cracks. FIG. 2 is a schematic cross-sectional view of a prefabricated part including a defect zone and a forming zone, as shown in FIG. 2, for each cross section, defect preparation powder and defect preparation process parameters are used to print specific layers in zone 10 defects, forming powder and corresponding process parameters are used to print specific layers in the forming zone 11.

Specifically, the particle size of the defect preparation powder is from 45 μm to 150 μm, where the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%. In one embodiment, the defect preparation powder is prepared by an atomization method by rotating the electrode in a plasma.

The defect preparation process parameters contain: laser power 450 W - 550 W, scanning speed 600 mm/min - 1200 mm/min, powder feed rate 4 g/min - 12 g/min, spot diameter 1 mm - 1.2 mm, pitch scanning 0.5 mm - 0.8 mm and layer thickness 0.08 mm - 0.2 mm.

The volume percentage of defects in the form of cracks in the defect zone is controlled by adjusting the parameters of the defect preparation process. Specifically, in one embodiment, the volume percentage of crack defects in the defect zone is controlled by adjusting the ratio of laser power to powder feed rate. In another embodiment, the method for adjusting the defect preparation process parameters is determined by trial and error, for example, parameter A is adjusted in the (N+1)th test, the volume percentage of crack defects prepared in the (N+1)th test, shows an increasing trend compared to the volume percentage of crack defects prepared in the Nth test, allowing a calibrated volume percentage to be obtained by continuously adjusting parameter A. In another embodiment, a parametric database may also be provided to record the change in the percentage of defects in in the form of cracks every time after adjusting the parameters of the defect preparation process, therefore, a certain proportion of defects in the form of cracks can be obtained by accessing the database to adjust the parameters of the defect preparation process.

Embedded crack defects can be naturally generated in each layer of the defect zone 10 printed using the above-mentioned defect preparation powder and defect preparation process parameters, thereby realizing the natural formation of crack defects in the prefabricated part 1. Since the crack defects are formed In this way, have a feature of the actual solidification process of the metal, a sign of continuity corresponding to the structure of the crack zone can be preserved in defects in the form of cracks. At the same time, the location of the zone where defects in the form of cracks are generated can be controlled by separating the defect zone and the formation zone, compared with the prior art, this method can ensure the generation of defects in the form of cracks by more accurately simulating the solidification process of laser melting deposition, without damage to the structure and characteristics of the product.

A prefabricated part with embedded crack defects prepared by this method has the advantage of analyzing the true correspondence between crack defects generated by laser fusion deposition additive manufacturing and non-destructive testing signals. Together with the test results, the product characteristics, the relationship between crack defects and product performance can be analyzed and investigated. Additionally, the relationship between built-in crack defects and additive manufacturing product reliability can be analyzed, providing strong theoretical support for the application of metal additive manufacturing forming, which has a broad research and application perspective.

In one or more embodiments, a plurality of defect zones 10 may be provided, so the 3D model needs to be divided into a plurality of defect zones and a formation zone in step S101, and the spherical powder proportion, the hollow powder proportion and defect preparation process parameters must be set separately for each zone defects at step S102. The technical problem of controlling the position and feature of the defect and defect zone in a prefabricated part during defect preparation can be solved by setting parameters for the defect zone. The defect zone is designed to simulate the defects and features of the actual part, which allows you to control the proportion of defects, the size of defects and the intensity of defects in different defect zones, and partitioning allows you to obtain defects with different features at different positions on the same part. Defect concentration often occurs during the forming process or part preparation process, so the preparation of a single defect cannot actually show the overall concentration of defects and the structural features of the defects and their surroundings, and cannot show the effectively prepared actual defects. Using the defect zone to simulate the generation of defects and their characteristics allows not only to simplify the method of preparing pre-fabricated defects, making it more convenient to use, but also to improve the accuracy of non-destructive testing for detecting defects with a pre-fabricated part as a standard part, to improve the accuracy of the relationship between defects and product characteristics, and improve the accuracy of the relationship between defects and product service life. In addition, when performing non-destructive testing of a prefabricated part, the sensitivity of prefabricated defects at different depths must be tested under the same non-destructive test conditions, defect partitioning allows defects to be generated at specific depths in one prefabricated part and not to be generated at a different depth, which can effectively avoid the influence on the test sensitivity due to differences in the composition and uniformity of different products, which improves the test accuracy, the influence of various characteristics of defects on different designs on the results of non-destructive testing can be analyzed, and the influence of defects in different positions and in various environmental conditions (temperature, voltage) on the characteristics of a pre-manufactured part. On the other hand, when preparing a prefabricated part with a specified defect position and characteristics (e.g., proportion, size and intensity), the defect preparation process to be used is determined by the number and size of the defect area. If multiple defect zones are provided, it is necessary to set formation strategies (eg, amount of heat of the shaping laser, formation sequence, formation path planning, layer separation, etc.) of the proportions of different defects for each defect zone.

As shown in FIG. 3, in one or more embodiments, a method for preparing a prefabricated part with embedded crack defects further comprises,

S103: process models of defect zone 10 and form zones 11 separated from the 3D model, where model processing comprises: tolerance adding processing, layer separation and cutting processing, and path planning processing. Specifically, the tolerance adding processing involves adding a printing tolerance to the outer peripheral contour in the defect zone 10 and the formation zone 11, respectively, so that the boundary of the defect zone 10 and the formation zone 11 can be bonded to each other by fusion, where the metallurgical bond can be achieved by the boundary of the melt pool of the two zones overlapping each other, or deposition with melting of the upper and lower layers of two zones. Layering and cutting processing consists of dividing a 3D scanned model into multiple layers by cutting, providing a basis for subsequent layer-by-layer printing. Path planning processing consists of planning a laser scanning path for each unit layer obtained after layer separation and cutting processing. Different powder feeders and laser generators can be used for the defect zone 10 and the formation zone 11 in each unit layer, and the defect zone 10 and the formation zone 11 can be printed sequentially or simultaneously.

In one or more embodiments, the method for preparing a prefabricated part with embedded crack defects further comprises S105: heat treatment of the printed prefabricated part 1 may particularly be a stress relief heat treatment or a structural adjustment solution treatment.

In one or more embodiments, the method of preparing a prefabricated part with embedded crack defects further comprises S106: remove the printed prefabricated part 1 from the substrates, in some embodiments, the prefabricated part 1 is printed on the substrates, so the prefabricated part 1 needs remove from substrates in one way or another, for example, with sharp wire after printing. In other embodiments, the prefabricated part 1 is not printed on substrates, in which case step S106 is not required.

In one or more embodiments, the method for preparing a prefabricated part with embedded crack defects further comprises S107: surface treatment of the printed prefabricated part 1, in particular, the prefabricated part 1 can be polished or machined to meet a surface quality requirement of the product.

In one or more embodiments, the forming powder in the prior art is a metal powder prepared in a standard process and having standard chemical and physical properties, and the corresponding process parameters are those commonly used in the industry for printing the forming powder, so in advance a manufactured part prepared with forming powder and appropriate process parameters will generate fewer or no defects such as cracks. In one embodiment, a powder material having a composition similar to or the same as the defect preparation powder used to prepare the defect zone 10 is typically selected as a standard powder to ensure bonding between the defect zone 10 and the formation zone 11.

A specific example of preparing a prefabricated part with built-in defects in the form of cracks in the manner described in the first embodiment is shown below, according to Figs. 1-3:

Powdered Hastelloy X alloy is selected as the preparation powder for the forming zone 11.

First of all, set the position of the prefabricated crack defect zone on the prefabricated part 1 as the center of the product, where the zone is a rectangular zone with a size of 15 mm × 7 mm × 5 mm, and the proportion of crack defects in the rectangular zone is set to about 0.2%-0.3%.

Then, based on the position and size of the embedded crack defects, divide the prefabricated defect zone from the 3D model of the additive manufacturing product through UG modeling software, forming a defect zone 10 and a formation zone 11 inside the prefabricated part 1.

Then, carry out layer separation and cutting processing and path planning processing in the inner zone of the prefabricated crack defects and the outer formation zone of the prefabricated part 1, where the melt pool boundary of the two zones overlaps with each other, which allows metallurgical bonding at the boundary to be achieved.

Then fill the area of prefabricated defects in the form of cracks inside the prefabricated part by additive manufacturing method based on laser melting deposition based on synchronous powder feeding, and the powder used is a powdered high-temperature alloy GH3536 prepared by atomization method by rotating the electrode in plasma, with the following weight percentages of the main chemical elements: Ni:46%, C:0.075%, Cr:22.0%, Co:1.5%, Mo:9.5%, W:0.7%, Fe:19.0%, Mn≤ 0.01%, Si≤0.1%, P≤0.008%, S≤0.0015%, O≤0.015%, N≤0.005%, and the remainder is other trace elements with particle size: 45μm ~ 150μm , the proportion of spherical powder with smooth surface is 95% and almost no hollow powder. Parameters of the defect preparation process: laser power 550 W, scanning speed 600 mm/min, powder feeding speed 12 g/min, spot diameter 1.2 mm, scanning step 0.8 mm and layer thickness 0.2 mm, due to which a zone is formed prefabricated crack defects of the current layer, and then the surrounding forming zone of the current layer can be formed using another powder feeder with normal forming process parameters for the forming zone.

Then heat treatment and structural regulation solution treatment are carried out according to the requirement of the product, in particular, the heat treatment process involves: using a vacuum heat treatment furnace, and the heat treatment speed is 1175°C/h, cooling in the furnace.

Then remove the product with prefabricated defects prepared by additive manufacturing from the substrate by wire cutting.

Finally, the product prepared by additive manufacturing is mechanically processed to meet the product surface quality requirement, Ra≤0.8 µm

After testing, the crack defect rate of the prefabricated defect zone prepared by this method is about 0.25% and the crack width is ＜45 µm.

FIG. 4 shows a polished metallographic morphology of crack defects on a prefabricated part prepared by the above-mentioned method, wherein the prefabricated part prepared by the above-mentioned method is provided with a plurality of naturally generated cracks 12, and the structure of two sides of the plurality of cracks 12 has the characteristic of corresponding continuity. .

Second embodiment

The second embodiment demonstrates a method for preparing a remanufactured part with embedded crack defects.

FIG. 5 is a schematic cross-sectional view of the defect area of a remanufactured part with embedded crack defects in this embodiment. In this embodiment, the repaired part 1a includes a part body 100a and a restoration zone 100b, wherein the restoration zone 100b is used to repair a defect in the part body 100a. FIG. 6 shows a schematic cross-sectional view of the recovery zone 100b. FIG. 7 shows a flowchart of a method for preparing a refurbished part shown in FIG. 5.

To prepare the repaired part 1a, S201 is first performed: obtain a 3D model of the repair area 100b based on the defect or damage of the part body 100a, wherein the 3D model of the repair area 100b can be obtained by 3D scanning, etc., the 3D model can be created in software 3D graphics processing, such as UG, AUTOCAD or other modeling software, and separated into the software.

Next, S203 is executed: obtain the part body 100a, specifically, according to the embodiment shown in FIG. 5, defects in the part body 100a may be casting defects, machining defects, or performance defects such as cracks, gouges, etc., and the restoration zone 100b is a restoration part provided in accordance with the potholes. Thus, the preparation method shown in FIG. 7 further comprises the steps of S200, obtain the finished part, and S202, cut the finished part, to proceed to S203 to obtain the part body 100a. The finished part may be a part that has aged after use, and the part body 100a is obtained by cutting out a damaged portion on the aged part. The finished part can also be produced by other means, such as additive manufacturing. The slot may have a trapezoidal shape, as shown in the figure, or another suitable shape, such as a U-shape or a V-shape, the angles of the sides of the slot being typically less than 60°, and the edges between the sides and the bottom being chamfered. According to an embodiment different from the steps shown in FIG. 7, the part body 100a can also be formed directly in the additive manufacturing process, where defects to be repaired will be formed simultaneously on the part body 100a when printed.

Then, as shown in Fig. 6, divide the 3D model of the restoration zone into at least one defect zone 10a and one formation zone 11a, in the case shown in Fig. 5, where the part is restored, the defect zone 10a is located inside the restored part 1a. Specifically, the defect area 10a is located at the position shown in the figure, which is downstream in the restoration direction of the restoration area 100b, so that when restoration is completed, the defect area 10a is located inside the repaired part 1a. In some other embodiments other than those shown in the figure, the defect zone 10a may be provided directly within the formation zone 11a.

Next, S204 is executed to set the volume percentage of built-in crack defects in the defect area 10a, wherein the volume percentage may be determined by the ratio of the volume of built-in crack defects in the actual repaired part to be modeled to the volume of the actual repaired part, that is, (volume of built-in cracks in the form of cracks/volume of the defect zone) * volume of the defect zone/volume of the prefabricated part=volume of built-in defects in the form of cracks in the actual restored part/volume of the actual restored part. The spherical powder proportion, hollow powder proportion and defect preparation process parameters can be adjusted according to the volume percentage of defects.

S206 is then performed: printing the restoration zone 100b layer by layer on the defect of the part body 100a, where for layers relative to the defect zone 10a, defect preparation powder and defect preparation process parameters are used to print specific layers in the defect zone, and forming powder and corresponding process parameters are used to printing specific layers in the formation zone 11a. In one embodiment, the printing tolerance needs to be added to the outer peripheral contour of the recovery zone 100b prior to printing, in order to achieve a strong metallurgical bond between the recovery zone 100b and the body of the part.

Specifically, the particle size of the defect preparation powder is from 45 μm to 150 μm, where the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%. In one embodiment, the defect preparation powder is prepared by an atomization method by rotating the electrode in a plasma.

The defect preparation process parameters contain: laser power 450 W - 550 W, scanning speed 600 mm/min - 1200 mm/min, powder feed rate 4 g/min - 12 g/min, spot diameter 1 mm - 1.2 mm, pitch scanning 0.5 mm - 0.8 mm and layer thickness 0.08 mm - 0.2 mm.

The volume percentage of defects in the form of cracks in the defect zone is controlled by adjusting the parameters of the defect preparation process. Specifically, in one embodiment, the volume percentage of crack defects in the defect zone is controlled by adjusting the ratio of laser power to scanning speed. In another embodiment, the method for adjusting the defect preparation process parameters is determined by trial and error, for example, parameter A is adjusted in the (N+1)th test, the volume percentage of crack defects prepared in the (N+1)th test, shows an increasing trend compared to the volume percentage of crack defects prepared in the Nth test, allowing a calibrated volume percentage to be obtained by continuously adjusting parameter A. In another embodiment, a parametric database may also be provided to record the change in the percentage of defects in in the form of cracks every time after adjusting the parameters of the defect preparation process, therefore, a certain proportion of defects in the form of cracks can be obtained by accessing the database to adjust the parameters of the defect preparation process.

In one or more embodiments, the method of preparing a prefabricated part with embedded crack defects further comprises,

S205: process the models of the defect area 10a and the formation area 11a separated from the 3D model of the restoration area 100b, where the model processing includes: tolerance adding processing, layer separation and cutting processing, and path planning processing. Specifically, the tolerance adding processing serves to add a printing tolerance to the outer peripheral contour for the defect area 10a and the formation area 11a separately, so that the boundary of the defect area 10a and the formation area 11a can be bonded to each other by fusion, where a metallurgical bond can be achieved by the boundary melt pools of two zones overlapping each other, or deposition with melting of the upper and lower layers of two zones. Layering and cutting processing consists of dividing a 3D scanned model into multiple layers by cutting, providing a basis for subsequent layer-by-layer printing. Path planning processing consists of planning a laser scanning path for each unit layer obtained after layer separation and cutting processing. Different powder feeders and laser generators can be used for the defect zone 10a and the formation zone 11a in each unit layer, and the defect zone 10a and the formation zone 11a can be printed sequentially or simultaneously.

In one or more embodiments, the method for preparing a prefabricated part with embedded crack defects further comprises S207: heat treatment of the printed repair part 1a may particularly be a stress relief heat treatment or a structural adjustment solution treatment.

In one or more embodiments, the method for preparing a prefabricated part with embedded crack defects further comprises S208: surface treating the printed prefabricated part, in particular, the refurbished part 1a can be polished or machined to meet a surface quality requirement of the product.

In one or more embodiments, the forming powder in the prior art is a metal powder prepared in a standard process and having standard chemical and physical properties, and the corresponding process parameters are those commonly used in the industry for printing the forming powder, so in advance a manufactured part prepared with forming powder and appropriate process parameters will generate fewer or no defects such as cracks. In one embodiment, the standard powder is typically selected to be a powder material having a composition similar to or the same as the defect preparation powder used to prepare the defect zone 10a to ensure bonding between the defect zone 10a and the formation zone 11a.

A specific example of preparing a repaired part 1a with embedded crack defects in the manner described in the second embodiment is shown below, according to Figs. 5-7:

GH3536 alloy powder is selected as the preparation powder for the reduction zone.

First of all, cut the damaged area where the notch is located on the forging product GH3536 by machining, and the shape of the slot is shown in Fig. 5, which is a trapezoidal slot with the inclination angles of the sides of the slot about 45° and the size of 17 mm top line, 10 mm bottom lines, 7 mm high and 7 mm wide, giving a body of 100a parts.

Then, obtain a 3D model of the restoration zone 100b by 3D scanning the cut zone,

then, set the vertical distance between the top surface of the crack defect zone 10a and the surface of the body 100a of the forging part GH3536 to be 17 mm, as shown in FIG. 5, and set the crack defect fraction of the prefabricated defect zone 10a to about 1, 45%-1.55%.

Then, based on the position and proportion of prefabricated crack defects, divide the 3D model of the trapezoidal slot into a lower defect zone 10a and an upper defect formation zone 11a by the CAD modeling software.

Then, carry out layer separation and cutting processing and path planning processing in the inner zone of the prefabricated crack defects and the outer zone of forming the repaired part 1a, where the melt pool boundary of the two zones overlaps with each other, allowing metallurgical bonding at the boundary to be achieved.

Add a print tolerance to the resulting 3D model of the prefabricated defect area, add a print tolerance of about half the spot diameter to the inclined sides of the trapezoidal slot, so that the sides of the trapezoidal slot and the body of the part can overlap and are strongly connected to each other, which then allows for layer separation processing and cutting and path planning processing on a 3D model of the lower zone of prefabricated defects in the form of cracks and the upper formation zone.

Then fill the area of prefabricated defects in the form of cracks inside the prefabricated part by additive manufacturing method based on laser melting deposition based on synchronous powder feeding, and the powder used is a powdered high-temperature alloy GH3536 prepared by atomization method by rotating the electrode in plasma, with the following weight percentages of the main chemical elements: Ni:49%，C:0.085%，Cr:22.5%，Co:2.0%，Mo:8.5%，W:0.5%，Fe:17.0%，Mn≤ 0.01%，Si≤0.1%，P≤0.008%，S≤0.0015%，O≤0.015%，N≤0.005%, and the remainder is other trace elements with particle size: 45μm ~ 150μm , the proportion of spherical powder with smooth surface is 95% and almost no hollow powder. The defect preparation process parameters were: laser power 450 W, scanning speed 1200 mm/min, powder feed rate 4 g/min, spot diameter 1 mm, scanning step 0.5 mm and layer thickness 0.08 mm. When filled to a predetermined height, the formation of the prefabricated crack defect zone is completed, and then the upper product forming zone will be formed using normal forming process parameters.

Then heat treatment of vacuum stress relief is carried out at a heat treatment speed of 650°C/4h, cooling in a furnace.

Finally, the surface of the prefabricated defect area prepared by additive manufacturing is polished to meet the product surface quality requirement, Ra≤0.6 μm.

After testing, the crack defect rate of the prefabricated defect zone of the remanufactured part on the forging product GH3536 prepared by laser melting deposition method is about 1.50%, and the crack width is ＜50 μm.

FIG. 8 shows a polished metallographic morphology of crack defects on a prefabricated part prepared by the above-mentioned method, wherein the prefabricated part prepared by the above-mentioned method is provided with a plurality of naturally generated cracks 12a, and the structure of the plurality of cracks 12a has a continuity feature. Since the ratio of laser power to powder feed rate in the second embodiment is smaller than that in the first embodiment, more crack defects are shown in FIG. 8 than in FIG. 4.

Simulating crack defects inside a remanufactured part with embedded crack defects is achieved according to the above embodiment, which makes it possible to obtain a remanufactured part with naturally generated crack defects to further analyze the relationship between the built-in crack defects and the reliability of the remanufactured part prepared by additive manufacturing, providing strong theoretical support for the application of metal additive manufacturing formation, which has a broad research and application perspective.

Although preferred embodiments of the present invention are disclosed above, they are not intended to limit the present invention. One skilled in the art may suggest any changes and modifications without departing from the spirit and scope of the present invention. Thus, any modifications, equivalent changes and embellishments to the above-described embodiments that do not go beyond the scope of the technical solution of the present invention based on the technical essence of the present invention are within the scope of protection specified by the claims.

Claims (55)

1. A method for preparing prefabricated defects in the form of cracks during the additive manufacturing of metal parts, characterized in that it contains stages in which: define the defect zone, set the volume percentage of defects in the form of cracks in the defect zone, adjust the proportion of spherical powder, the proportion of hollow powder and the parameters of the defect preparation process according to the volume percentage of defects in the form of cracks, based on the laser melting deposition method, the defect zone is printed layer by layer using the defect preparation powder and defect preparation process parameters, wherein the particle size of the defect preparation powder is from 45 to 150 μm, the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%, Moreover, the parameters of the defect preparation process contain: laser power 450-550 W, scanning speed 600-1200 mm/min, powder supply speed 4-12 g/min, spot diameter 1-1.2 mm, scanning step 0.5-0, 8 mm and layer thickness 0.08-0.2 mm. 2. The method according to claim 1, in which the volume percentage of defects in the form of cracks in the defect zone is controlled by adjusting the ratio of laser power P to scanning speed v, Moreover, when the P/v ratio decreases, the volume percentage of defects in the form of cracks in the defect zone increases. 3. A method for preparing a pre-fabricated part with built-in defects in the form of cracks, based on the laser melting deposition method, in the additive manufacturing of metal parts, characterized in that it contains stages in which: receive a 3D model of a pre-fabricated part, dividing the prefabricated part into at least one defect zone and one formation zone, wherein the defect zone is provided inside the prefabricated part, set the volume percentage of built-in defects in the form of cracks in the defect zone, adjust the proportion of spherical powder, the proportion of hollow powder and the parameters of the defect preparation process according to the volume percentage of defects in the form of cracks, a pre-fabricated part with built-in defects in the form of cracks is printed layer-by-layer, wherein the defect preparation powder and the parameters of the defect preparation process are used to print specific layers relative to the defect area, wherein the particle size of the defect preparation powder is from 45 to 150 μm, the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%, Moreover, the parameters of the defect preparation process contain: laser power 450-550 W, scanning speed 600-1200 mm/min, powder supply speed 4-12 g/min, spot diameter 1-1.2 mm, scanning step 0.5-0, 8 mm and layer thickness 0.08-0.2 mm. 4. The method according to claim 3, in which The 3D model of a prefabricated part is divided into multiple defect zones and a formation zone, and the proportion of spherical powder, the proportion of hollow powder and defect preparation process parameters are set separately for each defect zone. 5. The method according to claim 3, in which the volume percentage of defects in the form of cracks in the defect zone is controlled by adjusting the ratio of laser power P to scanning speed v, Moreover, when the P/v ratio decreases, the volume percentage of defects in the form of cracks in the defect zone increases. 6. The method according to claim 3, further comprising the step of: 3D models of the defect zone and the formation zone are processed, where the model processing contains: processing of adding a tolerance, layer separation and cutting processing and path planning processing. 7. The method according to claim 3, further comprising the steps of: thermally treat the printed pre-fabricated part, remove the printed prefabricated part from the substrates and treating the surface of the printed prefabricated part. 8. A pre-made part with built-in defects in the form of cracks, characterized in that it is prepared by the method according to any of claims 3-7. 9. A method for preparing a restored part with built-in defects in the form of cracks, based on a laser melting deposition method, in the additive manufacturing of metal parts, wherein the restored part contains a part body and a restoration zone, and the restoration zone is used to restore the defect or damage to the part body, wherein The method differs in that it contains the steps of: get a 3D model of the part body and restoration zone, respectively, receive the body parts, dividing the 3D model of the restoration zone into at least one defect zone and one formation zone, wherein the defect zone is provided inside the restored part after restoration, set the volume percentage of built-in defects in the form of cracks in the defect zone, adjust the proportion of spherical powder, the proportion of hollow powder and the parameters of the defect preparation process according to the volume percentage of defects in the form of cracks, printing the restoration zone on the defect of the part body layer by layer, and the defect preparation powder and the parameters of the defect preparation process are used to print specific layers relative to the defect zone, wherein the particle size of the defect preparation powder is from 45 to 150 μm, the proportion of spherical powder is ≥93% and the proportion of hollow powder is <0.5%, Moreover, the parameters of the defect preparation process contain: laser power 450-550 W, scanning speed 600-1200 mm/min, powder supply speed 4-12 g/min, spot diameter 1-1.2 mm, scanning step 0.5-0, 8 mm and layer thickness 0.08-0.2 mm. 10. The method according to claim 9, in which the volume percentage of defects in the form of cracks in the defect zone is controlled by adjusting the ratio of laser power P to scanning speed v, Moreover, when the P/v ratio decreases, the volume percentage of defects in the form of cracks in the defect zone increases. 11. The method of claim 9, wherein the defect in the body of the part includes casting defects, machining defects or operational defects, and the method further comprises the step of: cutting through the finished part to obtain the body of the part. 12. The method according to claim 9, further comprising the step of: 3D models of the defect zone and the formation zone of the restoration zone are processed, where the model processing contains: processing of adding a tolerance, layer separation and cutting processing and path planning processing. 13. The method according to claim 9, further comprising the steps of: thermally treat the printed restored part and the surface of the printed restored part is processed.

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